(1) Field of the invention
The present invention relates to a gas flow pass through which a gas and the other foreign substances including a solid member such as a metal plate and a liquid member such as water are passed.
(2) Related Art Statement
For example, in an exhaust gas flow pass of an internal combustion engine, solid members and liquid members are clashed against an inner wall of the exhaust gas flow pass, or a construction member arranged in the gas flow pass or connected with the gas flow pass at a high speed together with a gas flow, so that the inner wall of the gas flow pass or the construction member are broken. As the solid members, there are rust or welding scraps on an inner surface of the flow pass wall, dust inserted into the flow pass in the case of installation, and so on. As the liquid members, there are a condensed water and so on.
In these cases, in order to protect an inner wall 53 of a gas flow pass 51 shown in FIGS. 12a and 12b from the solid members and the liquid members, or to protect a honeycomb structural body 52 having a construction shown in FIG. 12c from a breakage, a metal net 54 shown in FIG. 12a or an protection member 55 shown in FIG. 12b is arranged at an upstream position of the gas flow pass or the honeycomb structural body 52.
However, even if the metal net 54 or the protection member 55 is arranged as mentioned above, it is not possible to eliminate completely the solid members and the liquid members, and thus a long term reliability of the gas flow pass is decreased. That is to say, a damage on the surface of the gas flow pass is generated due to foreign substances flowing from an upstream position of the gas flow pass. Moreover, a fracture of the construction member positioned at a downstream is generated due to foreign substances flowing from an upstream position of the gas flow pass. Further, in the case that the foreign substances flowing from an upstream position of the gas flow pass have a conductivity and are contacted with an electric circuit arranged in the gas flow pass, an electric short is liable to occur and thus a long term reliability of the gas flow pass can not be maintained.